Conventionally, a device that stops or decelerates an object in motion with friction, has been known. For example, JP 2011-012750 A discloses a braking device including a bearing including a frictional material, a shaft inserted into the bearing, and a unidirectional clutch that rotates the shaft only in one direction. The device generates friction between the shaft and the bearing upon normal rotation of the shaft. However, this is a configuration in which the friction between the shaft and the bearing also occurs upon reverse rotation of the shaft. Therefore, the device prevents the reverse rotation of the shaft, with the unidirectional clutch. According to the device, only when an object to be controlled (hereinafter, the object to be controlled is simply referred to as an “object”) rotates in the one direction, motion of the object can be stopped or decelerated. Performance in which motion of an object can be stopped or decelerated only when the object rotates in one direction, is referred to as “unidirectionality”, below.
However, the unidirectional clutch is required in order to regulate a rotational direction of the shaft in the conventional technique. Therefore, the amount of assembly man-hours inevitably also increases because of a large number of components. As a result, there is a problem that manufacturing costs are high. In addition, dimensional accuracy of the shaft to be integrated with the unidirectional clutch is high, and hardness of a surface of the shaft is required. Thus, there is a problem that processing costs of the shaft are high. Furthermore, there is a problem that providing the unidirectional clutch results in an increase of the device in size.